Because of decaying radioactive materials in the earth radon gas is present in the earth over many parts of the world. It has been determined that over extensive areas of the United States, radon accumulates in dwellings at dangerous levels exceeding the four picocuries per liter of air standard set by the Environmental Protection Agency. That agency reports that radon at this level is a carcinogenic gas equal in health risk to smoking half a pack of cigarettes daily. Homes along the Triassic Basin in Virginia showed radon levels as high as 100 pCi/l, a comparable annual lung cancer risk to 20,000 chest X-rays.
Conventional methods of protecting homes against radon gas are both expensive and uncertain. Since the gas may seep into basements through sump pumps and cracks, all such sources are sealed up. This however does not account for seepage through cement joints or porous building block walls underground. Nor does it prevent other new cracks from developing, so that assurance against return of radon gas is not possible by these methods, which can be very expensive in terms of renovation and repair. Also venting of basements and the like has been a conventional technique for removing accumulated radon out into the atmosphere, where it becomes so dilute that it is not a serious threat to human health.
A further problem confronting radon gas control in modern housing is the tendency to seal up the dwelling from escape of heat and air, and the lack of circulation of fresh air through the dwelling. This contributes to even greater concentration of radon gas, which tends to be held in fabrics and dust after it enters a dwelling, so that its removal by complete venting and replacement of air is inconsistent with present day homeowner psychology.
There are no known methods heretofore that can give assurance of radon gas protection, and particularly at relatively nominal capital outlays. It is therefore an objective of this invention to provide improved means and methods for control of radon gas in dwellings to assure that concentrations levels are in an acceptable range.